Network operators may seek to offer multicast based network services such as broadcast video, file sharing etc. to their end users. Multicast enabled networks usually employ a multicast routing protocol such as Protocol Independent Multicast (PIM) to build the multicast tree (such that the multicast source becomes the root and the multicast receivers become the leaves of the tree) in the network.
A Virtual Private Network (VPN) is a logical network that uses shared network infrastructure, such as the Internet, to provide dedicated and optionally secure communications to members of the VPN. A VPN may maintain privacy through agreed upon security procedures and protocols. Essentially, a VPN uses custom encryption to encrypt messages communicated via the VPN. The encryption and decryption of messages rely upon keys that are securely held by participants of the VPN.
A Dynamic Multipoint virtual private network (DMVPN) is an enhancement of the virtual private network (VPN) configuration process for routers. DMVPN makes use of Internet Protocol (IP) tunneling technique such as Generic Route Encapsulation (GRE) to tunnel the VPN traffic through the shared network infrastructure. A tunnel between two spoke routers may be created on an as needed basis. This alleviates the need for the hub router to route ‘unicast’ data between spoke networks, as was common in a non-fully meshed frame relay topology. However, this is not applicable to ‘multicast’ data.
Usage of multicasting in current DMVPN framework is limited to ‘hub and spoke’ topology by which the multicast traffic always involves the hub. While the current framework satisfies the general needs of a given networking model, using a non-broadcast multi-access (NBMA) technique puts a significant replication load on the hub router(s), particularly when the multicast source is located in a spoke site. Accordingly, the ability to minimize this load or to optimize these communications in the context of multicasting activities presents a significant challenge to network administrators, component manufacturers, and system designers alike.